High-frequency analog and digital signals (in the bandwidth of 10 GHz and above) are typically analyzed using a real-time digital oscilloscope or a sampling oscilloscope. However, both types of oscilloscope are expensive. Also, a real-time oscilloscope can introduce interpolation errors because the oscilloscope cannot acquire enough samples compared to the frequency content of the signal to be analyzed to make an accurate measurement. In addition, these oscilloscopes can require an external clock, a recovered clock, knowledge of the signal frequency, or an external trigger signal synchronous with the analyzed signal in order to appropriately analyze a signal. It would be useful to be able to analyze these signals using a less expensive device without requiring knowledge of the signal frequency or having a synchronized trigger signal.